Isomerization of naphthenes

ABSTRACT

Isomerizable hydrocarbons are isomerized using a catalyst comprising a combination of a platinum group component, a cobalt component, a tin component and a halogen component with a porous carrier material. The cobalt and platinum group components are reduced to the metallic state while the tin is present in a positive oxidation state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of our co-pending application Ser. No.633,889 filed Nov. 20, 1975 now U.S. Pat. No. 4,013,738 which is acontinuation-in-part of our application Ser. No. 522,209 filed Nov. 8,1974, now U.S. Pat. No. 3,959,988 the teachings of which areincorporated herein by specific reference thereto.

FIELD OF THE INVENTION

This invention relates to a catalyst and process for isomerizingisomerizable hydrocarbons including isomerizable paraffins,cycloparaffins, olefins and alkylaromatics. More particularly, thisinvention relates to a process for isomerizing hydrocarbons with acatalyst comprising a combination of a platinum group component, acobalt component, a tin component and a halogen component with a porouscarrier material. The present invention uses a dual-function catalysthaving both a hydrogenation-dehydrogenation function and a crackingfunction which affords substantial improvements in hydrocarbonisomerization processes that have traditionally used dual-functioncatalysts.

Processes for the isomerization of hydrocarbons have acquiredsignificant importance within the petrochemical and petroleum refiningindustry. The demand for para-xylene has created a demand for processesto isomerize other xylene isomers and ethylbenzene to producepara-xylene. The demand for certain branched chain paraffins, such asisobutane or isopentane, as intermediates in producing high octane motorfuel alkylate, can be met by isomerizing the corresponding normalparaffins. It is desired that the alkylate be highly branched to providea high octane rating. This can be accomplished by alkylating anisoparaffin with C₄ -C₇ internal olefins which, in turn, can be producedby isomerization of corresponding linear alpha-olefins.

Catalytic composites exhibiting a dual hydrogenation-dehydrogenation andcracking function are widely used in the petroleum and petrochemicalindustry to isomerize hydrocarbons. Such catalysts generally have aheavy metal component e.g., metals or metallic compounds of Group Vthrough VIII of the Periodic Table, to impart ahydrogenation-dehydrogenation function, with an acid-acting inorganicoxide to impart a cracking function. In catalysis of isomerizationreactions, it is important that the catalytic composite not onlycatalyze the specific desired isomerization reaction by having its dualhydrogenation-dehydrogenation function correctly balanced against itscracking function, but also that the catalyst perform its desiredfunctions well over prolonged periods of time.

The performance of a given catalyst in a hydrocarbon isomerizationprocess is typically measured by the activity, selectivity, andstability of the catalyst. Activity refers to the ability of a catalystto isomerize the hydrocarbon reactants into the corresponding isomers ata specified set of reaction conditions; selectivity refers to thepercent of reactants isomerized to form the desired isomerized productand/or products; stability refers to the rate of change of theselectivity and activity of the catalyst.

The principal cause of instability (i.e., loss of selectivity andactivity in an originally selective, active catalyst) is the formationof coke on the catalytic surface of the catalyst during the reaction.This coke is characterizable as a high molecular weight,hydrogen-deficient, carbonaceous material, typically having an atomiccarbon to hydrogen ratio of about 1 or more. Thus, a problem in thehydrocarbon isomerization art is the development of more active andselective composites not sensitive to the carbonaceous materials and/orhaving the ability to suppress the rate of formation of thesecarbonaceous materials on the catalyst. A primary aim of the art is todevelop a hydrocarbon isomerization process utilizing a dual-functioncatalyst having superior activity, selectivity and stability. Inparticular, it is desired to provide a process wherein hydrocarbons areisomerized without excess cracking or other decomposition reactionswhich lower the overall yield of the process and make it more difficultto operate.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a process for isomerizingisomerizable hydrocarbons. It is another object of this invention toprovide an isomerization process using a particular isomerizationcatalyst effective in isomerizing isomerizable hydrocarbons withoutintroducing undesired decomposition and/or cracking reactions. It is afurther object of this invention to provide a process for isomerizingisomerizable hydrocarbons utilizing a dual-function catalyst havingsuperior activity, selectivity and stability.

It is also an object of the present invention to provide an improvedisomerization catalyst.

Accordingly, the present invention provides a catalyst comprising aporous carrier material containing, on an elemental basis, 0.01 to 2 wt.% platinum group metal, 0.1 to 5 wt. % cobalt, 0.01 to 5 wt. % tin and0.1 to 10 wt. % halogen, and about 1 to 100 wt. % of a Friedel-Craftsmetal halide calculated on a Friedel-Crafts metal halide free basis,wherein the platinum group metal cobalt and tin are uniformly dispersedthroughout the porous carrier material, wherein substantially all of theplatinum group metal and cobalt are present in the elemental metalicstate and substantially all of the tin is present in an oxidation stateabove that of the elemental metal.

In another embodiment, the present invention provides a process forisomerizing an isomerizable hydrocarbon which comprises contacting saidhydrocarbon at isomerization conditions with a catalyst comprising aporous carrier material containing, on an elemental basis, 0.01 to 2 wt.% platinum group metal, 0.1 to 5 wt. % cobalt, 0.01 to 5 wt. % tin and0.1 to 10 wt. % halogen, wherein substantially all of the platinum groupmetal, cobalt and tin are uniformly dispersed throughout the porouscarrier material, wherein substantially all of the platinum group metaland cobalt are present in the elemental metallic state and whereinsubstantially all of the tin is present in an oxidation state above thatof the elemental metal.

DETAILED DESCRIPTION

The process of this invention is applicable to the isomerization ofisomerizable saturated hydrocarbons including acyclic paraffins andnaphthenes and is particularly suitable for the isomerization ofstraight chain or mildly branched chain paraffins containing 4 or morecarbon atoms per molecule such as normal butane, normal pentane, normalhexane, normal heptane, normal octane, etc., and mixtures thereof.Cycloparaffins applicable are those containing at least 5 carbon atomsin the ring such as alkylcyclopentanes and cyclohexanes, includingmethylcyclopentane, dimethylcyclopentane, cyclohexane,methylcyclohexane, dimethylcyclohexane, etc. This process also appliesto the conversion of mixtures of paraffins and/or naphthenes such asthose derived by selective fractionation and distillation ofstraight-run natural gasolines and naphthas. Such mixtures of paraffinsand/or naphthenes include the so-called pentane fractions, hexanefractions and mixtures thereof. It is not intended, however, to limitthis invention to these enumerated saturated hydrocarbons and it iscontemplated that straight or branched chain saturated hydrocarbons andnaphthenes containing up to about 20 carbon atoms per molecule may beisomerized according to the process of the present invention with C₄ -C₉acyclic saturated hydrocarbons and C₅ -C₉ cycloparaffins beingparticularly preferred.

The olefins applicable within this isomerization process are generally amixture of olefinic hydrocarbons of approximately the same molecularweight, including the 1-isomer, 2-isomer and other position isomers,capable of undergoing isomerization to an olefin in which the doublebond occupies a different position in the hydrocarbon chain. The processof this invention can be used to provide an olefinic feedstock for motorfuel alkylation purposes containing an optimum amount of the morecentrally located double bond isomers, by converting the 1-isomer, orother near-terminal-position isomer into olefins wherein the double bondis more centrally located in the carbon atoms chain. The process of thisinvention is applicable to the isomerization of such isomerizableolefinic hydrocarbons as 1-butene to 2-butene or 3-methyl-1-butene to2-methyl-2-butene. The process of this invention can be utilized toshift the double bond of an olefinic hydrocarbon such as 1-pentene,1-hexene, 2-hexene, or 4-methyl-1-pentane to a more centrally locatedposition so that 2-pentene, 2-hexene, 3-hexene or 4-methyl-2-pentene,respectively, can be obtained. It is not intended to limit thisinvention to the enumerated olefinic hydrocarbons. It is contemplatedthat shifting the double bond to a different position may be effectivein straight or branched chain olefinic hydrocarbons containing from 4 upto about 20 carbon atoms per molecule. The process of this inventionalso applies to the hydroisomerization of olefins wherein olefins areconverted to branched-chain paraffins and/or branched olefins.

The process of this invention is also applicable to the isomerization ofisomerizable alkylaromatic hydrocarbons, e.g., ortho-xylene,meta-xylene, para-xylene, ethylbenzene, the ethyltoluenes, thetrimethylbenzenes, the diethylbenzenes, the triethylbenzenes, normalpropylbenzene, isopropylbenzene, etc., and mixtures thereof. Preferredisomerizable alkylaromatic hydrocarbons are the alkylbenzenehydrocarbons, particularly the C₈ alkylbenzenes, and non-equilibriummixtures of various C₈ aromatic isomers. Higher molecular weightalkylaromatic hydrocarbons such as the alkylnaphthalenes, thealkylanthracenes, the alkylphenanthrenes, etc., are also suitable.

The isomerizable hydrocarbons may be utilized as found in selectivefractions from various naturally-occurring petroleum streams, e.g., asindividual components or as certain boiling range fractions obtained bythe selective fractionation and distillation of catalytically crackedgas oil. The process of this invention may be utilized for completeconversion of isomerizable hydrocarbons when they are present in minorquantities in various fluid or gaseous streams. The isomerizablehydrocarbons for use in the process of this invention need not beconcentrated. For example, isomerizable hydrocarbons appear in minorquantities in various refinery offstreams, usually diluted with gasessuch as hydrogen, nitrogen, methane, ethane, propane, etc. Theseoffstreams, containing minor quantities of isomerizable hydrocarbons,are obtained from various refinery installations, including thermalcracking units, catalytic cracking units, thermal reforming units,coking units, polymerization units, dehydrogenation units, etc., andhave in the past been burned as fuel, since an economical process forthe utilization of the hydrocarbon content has not been available. Thisis particularly true of refinery fluid streams which contain minorquantities of isomerizable hydrocarbons. The process of this inventionallows the isomerization of aromatic streams such as reformate toproduce xylenes, particularly para-xylene, thus upgrading the reformatefrom its gasoline value to a high petrochemical value.

As hereinbefore indicated, the catalyst utilized in the process of thepresent invention comprises a porous carrier material or support havingcombined therewith catalytically effective amounts of a platinum groupcomponent, a cobalt component, a tin component, and a halogen componentwith a porous carrier material.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the isomerization process, and it is intendedto include within the scope of the present invention carrier materialswhich have traditionally been utilized in dual-function hydrocarbonconversion catalysts such as: (1) activated carbon, coke or charcoal;(2) silica or silica gel, silicon carbide, clays and silicates includingthose synthetically prepared and naturally occurring, which may or maynot be acid treated, for example, attapulgus clay, china clay,diatomaceous earth, fuller's earth, kaolin, kieselguhr, etc.; (3)ceramics, porcelain, crushed firebrick, bauxite; (4) refractor inorganicoxides such as alumina, titanium dioxide, zirconium dioxide, chromiumoxide, beryllium oxide, vanadium oxide, cesium oxide, hafnium oxide,zinc oxide, magnesia, boria, thoria, silica-alumina, silica-magnesia,chromia-alumina, alumina-boria, silica-zirconia, etc.; (5) crystallinezeolitic aluminosilicates such as naturally occurring or syntheticallyprepared mordenite and/or faujasite, either in the hydrogen form or in aform which has been treated with multivalent cations; (6) spinels suchas MgAl₂ O₄, FeAl₂ O₄, ZnAl₂ O₄, MnAl₂ O₄, CaAl ₂ O₄ and other likecompounds having the formula MO·Al₂ O₃, where M is a metal having avalence of 2; and, (7) combinations of elements from one or more ofthese groups. The preferred porous carrier materials for use in thepresent invention are refractory inorganic oxides, with best resultsobtained with an alumina carrier material. Suitable alumina materialsare the crystalline aluminas known as gamma-, eta-, and theta-alumina,with gamma- or eta-alumina giving best results. In addition, in someembodiments the alumina carrier material may contain minor proportion ofother well known refractory inorganic oxides such as silica, zirconia,magnesia, etc.; however, the preferred support is substantially puregamma- or eta-alumina. Preferred carrier materials have an apparent bulkdensity of about 0.3 to about 0.7 g/cc and surface area characteristicssuch that the average pore diameter is about 20 to 300 Angstroms, thepore volume is about 0.1 to about 1 cc/g and the surface area is about100 to about 500 m² /g. In general, best results are typically obtainedwith a gamma-alumina carrier material which is used in the form ofspherical particles having: a relatively small diameter (i.e., typicallyabout 1/16 inch), an apparent bulk density of about 0.3 to about 0.8g/cc, a pore volume of about 0.4 ml/g and a surface area of about 200 m²/g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere; and alumina spheres may becontinuously manufactured by the well known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

One essential constituent of the improved trimetallic composite used inthe present invention is a tin component, and it is an essential featureof the present invention that substantially all of the tin component inthe composite is in an oxidation state abovethat of the elemental metal.That is, it is believed that best results are obtained whensubstantially all of the tin component exists in the catalytic compositein the +2 or +4 oxidation state. Accordingly, the tin component will bepresent in the composite as a chemical compound such as the oxide,sulfide, halide, oxyhalide, oxysulfide and the like, wherein the tinmoiety is in a positive oxidation state, or in chemical combination withthe carrier material in a manner such that the tin component is in apositive oxidation state. Controlled reduction experiments with thecatalytic composites produced by the preferred methods of preparing theinstant catalytic composite have established that the tin component inthese catalysts is in a positive oxidation state and is not reduced bycontact with hydrogen at temperatures in the range of 1000° to 1200° F.It is important to note that this limitation on the oxidation state ofthe tin component requires extreme care in preparation and use of thepresent catalyst to insure that it is not subjected to a reducingatmosphere at temperatures above 1200° F. Equally significant is ourobservation that it is only when the tin component is in a uniformlydispersed state in the carrier material that it has the capability tomaintain its positive oxidation state when subjected to hereinafterdescribed prereduction step. Stated another way, if the tin component isnot properly dispersed on the support it can be reduced in theprereduction step and result in an inferior catalyst. Based on theevidence currently available it is believed that best results areobtained when the tin component is present in the catalyst as tin oxide.The term "tin oxide" as used herein refers to a coordinated tin-oxygencomplex which is not necessarily stoichiometric.

Interrelated with this oxidation state limitation are the factors ofdispersion of the tin component in the support and of particle size ofthe tin component. This interrelationship emanates from the observationthat it is only when the tin component is uniformly dispersed throughoutthe carrier material in a particle having a maximum chord length lessthan 100 Angstroms that it can successfully maintain its preferredoxidation state when it is subjected to a high temperature prereductiontreatment as hereinafter described. Thus in a preferred embodiment ofour invention, the instant multimetallic catalytic composite is preparedin a manner selected to meet the stated particle size and uniformdispersion limitations. By the use of the expression "uniform dispersionof the tin component in the carrier material" it is intended to describethe situation where the concentration of the tin ingredient isapproximately the same in any reasonably divisable portion of thecarrier material. Similarly, the expression "particles having a maximumchord length less than 100 Angstroms" is intended to denote particlesthat would pass through a sieve having a 100 Angstrom mesh size if itwere possible to make such a sieve.

The tin component may be incorporated into the catalytic composite inany sui table manner known to effectively disperse this componentthroughout the carrier material in the required particle size. Thus thiscomponent may be added to the carrier by coprecipitation or cogellationof a suitable soluble tin salt with the carrier material, byion-exchange of suitable tin ions with ions contained in the carriermaterial when the ion exchange sites are uniformly distributedthroughout the carrier or controlled impregnation of the carriermaterial with a suitable soluble tin salt under conditions selected toresult in penetration of all sections of the carrier material by the tincomponent. One preferred method of incorporating the tin componentinvolves coprecipitating it during the preparation of the preferredcarrier material, alumina. This method typically involves the additionof a suitable soluble tin compound such as stannous or stannic chlorideto an alumina hydrosol, mixing these ingredients to obtain a uniformdistribution of the tin moiety throughout the sol and then combining thehydrosol with a suitable gelling agent and dropping the resultingmixture into an oil bath, etc., as explained in detail hereinbefore.After drying and calcining the resulting gelled carrier material thereis obtained an intimate combination of alumina and tin oxide having therequired dispersion and particle size. Another preferred method ofincorporating the tin component into the catalytic composite involvesutilization of a soluble, decomposable compound of tin to impregnate theporous carrier material. In general, the solvent used in thisimpregnation step is selected on the basis of the capability to dissolvethe desired tin compound and to hold the tin moiety in solution until itis evenly distributed throughout the carrier material and is preferablyan aqueous, rather strongly acidic solution. Thus the tin component maybe added to the carrier material by commingling the latter with anaqueous solution of a suitable tin salt or suitable compound of tin suchas stannous bromide, stannous chloride, stannic chloride, stannicchloride pentahydrate, stannic chloride diamine, stannic trichloridebromide, stannic chromate, stannous fluoride, stannic fluoride, stanniciodide, stannic sulfate, stannic tartrate and the like compounds. Theacid used in the impregnation solution may be any organic or inorganicacid that is capable of maintaining the pH of the impregnation solutionin the range of about -1 or less to about 3 and preferably less than 1during the impregnation step and that does not contaminate the resultantcatalyst. Suitable acids are: inorganic acids such as hydrochloric acid,nitric acid and the like; and strongly acidic organic acids such asoxalic acid, malonic acid, citric acid and the like. A particularlypreferred impregnation solution comprises stannic or stannous chloridedissolved in a hydrochloric acid solution containing HCl in an amountcorresponding to at least about 5 weight percent of the carrier materialwhich is to be impregnated. Another useful impregnation solution isstannous or stannic chloride dissolved in an anhydrous alcohol such asethanol. In general, the tin component can be incorporated either priorto, simultaneously with, or after the other metallic components areadded to the carrier material. However, we have found that excellentresults are obtained when the tin component is incorporatedsimultaneously with the platinum group component and cobalt component.

Regardless of which tin compound is used in the preferred impregnationstep, it is essential that the tin component be uniformly distributedthroughout the carrier material. In order to achieve this objective withan aqueous impregnation solution it is necessary to dilute theimpregnation solution to a volume which is approximately equal to orsubstantially in excess of the void volume of the carrier material whichis impregnated and to add a relatively strong acid such as hydrochloricacid, nitric acid and the like to the impregnation solution in an amountcalculated to maintain the pH of the impregnation solution in a range ofabout -1 or less to about 3, preferably less than 1. It is preferred touse a volume ratio of impregnation solution to carrier material of atleast 0.5:1 and preferably about 1:1 to about 10:1 or more. Similarly,it is preferred to use a relatively long contact time during theimpregnation step ranging from about one-fourth hour up to aboutone-half hour or more drying to remove excess solvent in order to insurea high dispersion of the tin component into the carrier material. Thecarrier material is, likewise, preferably constantly agitated duringthis preferred impregnation step.

Regarding the amount of the tin component contained in the instantcomposite, it is preferably sufficient to constitute about 0.01 to about5 weight percent of the final composite, calculated on an elementalbasis, although substantially higher amounts of tin may be utilized insome cases. Best results are typically obtained with about 0.1 to about1 weight percent tin.

A second essential ingredient of the subject catalyst is the platinumgroup component, i.e., platinum, iridium, osmium, ruthenium, rhodium,palladium or mixtures thereof as a second component of the presentcomposite. It is an essential feature of the present invention thatsubstantially all of this platinum group component exists within thefinal catalytic composite in the elemental metallic state. Generally,the amount of this component present in the final catalytic composite issmall compared to the qualities of the other components combinedtherewith. In fact, the platinum group component generally will compriseabout 0.01 to about 2 weight percent of the final catalytic composite,calculated on an elemental basis. Excellent results are obtained whenthe catalyst contains about 0.05 to about 1 weight percent of platinumor palladium metal.

This platinum group component may be incorporated in the catalyticcomposite in any suitable manner known to result in a relatively uniformdistribution of this component in the carrier material such ascoprecipitation or cogellation, ion exchange or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum or palladium to impregnatethe carrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloropalladic acid. Otherwater-soluble platinum group compounds which may be used includechloriridic acid, rhodium trichloride, ammonium chloroplatinate,bromoplatinic acid, platinum trichloride, platinum tetrachloridehydrate, platinum dichlorocarbonyl dichloride, dinitrodiaminoplatinum,sodium tetranitroplatinate (II), palladium chloride, palladium nitrate,palladium sulfate, diammine palladium (II) hydroxide, tetramminepalladium (II) chloride, etc. The utilization of a platinum or palladiumchloride compound, such as chloroplatinic or chloropalladic acid, ispreferred since it facilitates the incorporation of both the platinum orpalladium component and at least a minor quantity of the halogencomponent in a single step. Hydrogen chloride or the like acid is alsogenerally added to the impregnation solution in order to furtherfacilitate the incorporation of the halogen component and the uniformdistribution of the metallic components throughout the carrier material.In addition, it is generally preferred to impregnate the carriermaterial after it has been calcined in order to minimize the risk ofwashing away the valuable platinum group compounds; however, in somecases it may be advantageous to impregnate the carrier material when itis in a gelled state.

Yet another essential ingredient of the present catalytic composite is acobalt component. Although this component may be initially incorporatedinto the composite in many different decomposable forms which arehereinafter stated, our basic finding is that the catalytically activestate for hydrocarbon conversion with this component is the elementalmetallic state. Consequently, it is a feature of our invention thatsubstantially all of the cobalt component exists in the catalyticcomposite either in the elemental metallic state or in a state which isreducible to the elemental state under hydrocarbon conversionconditions. Examples of this last state are obtained when the cobaltcomponent is initially present in the form of cobalt oxide, halide,oxyhalide, and the like reducible compounds. As a corollary to thisbasic finding on the active state of the cobalt component, it followsthat the presence of cobalt in forms which are not reducible athydrocarbon conversion conditions is to be scrupulously avoided if thefull benefits of the present invention are to be realized. Illustrativeof these undesired forms are cobalt sulphide and the cobalt oxysulphurcompounds such as cobalt sulphate. Best results are obtained when thecomposite initially contains all of the cobalt component in theelemental metallic state or in a reducible oxide state or in a mixtureof these states. All available evidence indicates that the preferredpreparation procedure specifically described in Example I results in acatalyst having the cobalt component in a reducible oxide form.

The cobalt component may be incorporated into the catalytic composite inany suitable manner known to those skilled in the catalyst formulationart to result in a relatively uniform distribution of cobalt in thecarrier material such as coprecipitation cogellation, ion-exchange,impregnation, etc. In addition, it may be added at any stage of thepreparation of the composite -- either during preparation of the carriermaterial or thereafter -- since the precise method of incorporation usedis not deemed to be critical. However, best results are obtained whenthe cobalt component is relatively uniformly distributed throughout thecarrier material in a relatively small particle or crystallite sizehaving a maximum dimension of less than 100 Angstroms, and the preferredprocedures are the ones that are known to result in a composite having arelatively uniform distribution of the cobalt moiety in a relativelysmall particle size. One acceptable procedure for incorporating thiscomponent into the composite involves cogelling or coprecipitating thecobalt component during the preparation of the preferred carriermaterial, alumina. This procedure usually comprehends the addition of asoluble, decomposable, and reducible compound of cobalt such as cobaltchloride or nitrate to the alumina hydrosol before it is gelled. Theresulting mixture is then finished by conventional gelling, aging,drying and calcination steps as explained hereinbefore. One preferredway of incorporating this component is an impregnation step wherein theporous carrier material is impregnated with a suitable cobalt-containingsolution either before, during or after the carrier material is calcinedor oxidized. The solvent used to form the impregnation solution may bewater, alcohol, ether or any other suitable organic or inorganic solventprovided the solvent does not adversely interact with any of the otheringredients of the composite or interfere with the distribution andreduction of the cobalt component. Preferred impregnation solutions areaqueous solutions of water-soluble, decomposable, and reducible cobaltcompounds. Best results are ordinarily obtained when the impregnationsolution is an aqueous solution of cobalt chloride or cobalt nitrate.This cobalt component can be added to the carrier material, either priorto, simultaneously with, or after the other metallic components arecombined therewith. Best results are usually achieved when thiscomponent is added simultaneously with the platinum group component viaan acidic aqueous impregnation solution.

The cobalt component should comprise, on an elemental basis, about 0.1to 5 weight percent of the finished catalyst, and preferably about 0.5to 2 weight percent.

It is essential to incorporate a halogen component into the trimetalliccatalytic composite of the present invention. Although the precise formof the chemistry of the association of the halogen component with thecarrier material is not entirely known, it is customary in the art torefer to the halogen component as being combined with the carriermaterial, or with the other ingredients of the catalyst in the form ofthe halide (e.g., as the chloride). This combined halogen may be eitherfluorine, chlorine, iodine, bromine, or mixtures thereof. Of these,fluorine and particularly chlorine are preferred for the purposes of thepresent invention. The halogen may be added to the carrier material inany suitable manner, either during preparation of the support or beforeor after the addition of the other components. For example, the halogenmay be added, at any stage of the preparation of the carrier material orto the calcined carrier material, as an aqueous solution of a suitable,decomposable halogen-containing compound such as hydrogen fluoride,hydrogen chloride, hydrogen bromide, ammonium chloride, etc. The halogencomponent or a portion thereof, may be combined with the carriermaterial during the impregnation of the latter with the platinum groupmetal and cobalt components; for example, through the utilization of amixture of chloroplatinic acid and hydrogen chloride. In anothersituation, the alumina hydrosol which is typically utilized to form thepreferred alumina carrier material may contain halogen and thuscontribute at least a portion of the halogen component to the finalcomposite. The halogen will be typically combined with the carriermaterial in an amount sufficient to result in a final composite thatcontains about 0.1 to about 10% and preferably about 1 to about 5%, byweight, or halogen, calculated on an elemental basis. It is to beunderstood that the specified level of halogen component in the instantcatalyst can be achieved or maintained during use in the presentisomerization process by continuously or periodically adding to thereaction zone a decomposable halogen-containing compound such as anorganic chloride (e.g., ethylene dichloride, carbon tetrachloride,t-butyl chloride) in an amount of about 1 to 100 wt. ppm. of thehydrocarbon feed, and preferably about 1 to 10 wt. ppm.

Regarding the preferred amounts of the various metallic components ofthe subject catalyst, we have found it to be a good practice to specifythe amounts of the cobalt component and the tin component as a functionof the amount of the platinum group metal component. On this basis, theamount of the cobalt component is ordinarily selected so that the atomicratio of cobalt to platinum group metal contained in the composite isabout 0.8:1 to 66:1 with the preferred range being about 1.6:1 to 18:1.Similarly, the amount of tin component is ordinarily selected to producea composite containing an atomic ratio of tin to platinum group metal ofabout 0.1:1 to about 13:1, with the preferred range being about 0.3:1 toabout 5:1.

Another significant parameter for the instant catalyst is the "totalmetals content" which is defined to be the sum of the platinum groupcomponent, the cobalt component and the tin component, calculated on anelemental basis. Good results are ordinarily obtained with the subjectcatalyst when this parameter is fixed at a value of about 0.15 to about5 weight percent, with best results ordinarily achieved at a metalsloading of about 0.3 to about 3 weight percent.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the final catalyst generallywill be dried at a temperature of about 90° to about 310° C for a periodof at least about 2 to about 24 hours or more, and finally calcined oroxidized at a temperature of about 375° to about 600° C in an air oroxygen atmosphere for a period of about 0.5 to about 10 hours in orderto convert substantially all of the metallic components substantially tothe oxide form. Because a halogen component is utilized in the catalyst,best results are generally obtained when the halogen content of thecatalyst is adjusted during the calcination step by including a halogenor a halogen-containing compound such as HCl in the air or oxygenatmosphere utilized. In particular, when the halogen component of thecatalyst is chlorine, it is preferred to use a mole ratio of water tohydrogen chloride of about 5:1 to about 100:1 during at least a portionof the calcination step in order to adjust the final chlorine content ofthe catalyst to a range of about 0.1 to about 10 weight percent.

An optional ingredient for the trimetallic catalyst of the presentinvention is a Friedel-Crafts metal halide component. Suitable metalhalides of the Friedel-Crafts type include aluminum chloride, aluminumbromide, ferric chloride, ferric bromide, zinc chloride and the likecompounds, with the aluminum halides and particularly aluminum chlorideordinarily yielding best results. Generally, this optional ingredientcan be incorporated into the composite of the present invention by wayof the conventional methods for adding metallic halides of this type;however, best results are ordinarily obtained when the metallic halideis sublimed onto the surface of the carrier material according to thepreferred method disclosed in U.S. Pat. No. 2,999,074, which isincorporated by reference.

In the preferred method, wherein the calcined composite is impregnatedwith a Friedel-Crafts metal halide component, the presence of chemicallycombined hydroxyl groups in the refractory inorganic oxide allows areaction to occur between the Friedel-Crafts metal halide and thehydroxy group of the carrier material. For example, aluminum chloridereacts with the hydroxyl groups of the preferred alumina carriermaterial to yield Al-O-AlCl₂ active centers which enhance the catalyticbehavior of the composite. Since chloride ions and hydroxyl ions occupysimilar sites on the carrier surface more hydroxyl sites will beavailable for possible interaction with the Friedel-Crafts metal halidewhen the chloride population of the carrier sites is low. Therefore,potentially more active Friedel-Crafts type versions of the catalystwill be obtained when the chloride content of the carrier material is inthe low range of the 0.1 to 10 weight range. Some halogen must bepresent on the carrier material at all times, however, to maintainproper dispersion of the other active elements.

The Friedel-Crafts metal halide may be impregnated onto the calcinedcomposite containing combined hydroxyl groups by the sublimation of theFriedel-Crafts metal halide onto the calcined composite under conditionssuch that the sublimed Friedel-Crafts metal halide is combined with thehydroxyl groups of the calcined composite. This reaction is typicallyaccompanied by the elimination of about 0.5 to about 2.0 moles ofhydrogen chloride per mole of Friedel-Crafts metal halide reacted withthe carrier material. For example, in the case of subliming alumiumchloride, which sublimes at about 184° C, suitable impregnationtemperatures range from about 190° C to about 700° C, with a preferablerange being between about 200° C and about 600° C. The sublimation canbe conducted at atmospheric pressure or under increased pressure and inthe presence of diluent gases such as hydrogen or light paraffinichydrocarbons or both. The impregnation of the Friedel-Crafts metalhalide may be conducted batch wise, but a preferred method forimpregnating the calcined composite is to pass sublimed AlCl₃ vapors, inadmixture with a carrier gas such as hydrogen, through a calcinedcatalyst bed. This method both continuously deposits and reacts thealuminum chloride and also removes the evolved HCl.

The amount of Friedel-Crafts metal halide combined with the calcinedcomposite may range from about 1 weight percent up to about 100 weightpercent of the Friedel-Crafts metal halide-free, calcined composite. Thefinal composite containing the sublimed Friedel-Crafts metal halide istreated to remove the unreacted Friedel-Crafts metal halide bysubjecting the composite to a temperature above the sublimationtemperature of the Friedel-Crafts metal halide for a time sufficient toremove from the composite any unreacted Friedel-Crafts metal halide. Inthe case of AlCl₃, temperatures of about 400° C to about 600° C, andtimes of from about 1 to about 48 hours are sufficient.

In a preferred embodiment of the present invention, the resultantoxidized catalytic composite is subjected to a substantially water-freeand hydrocarbon-free reduction step prior to its use in the conversionof hydrocarbons. This step is designed to selectively reduce theplatinum or palladium and cobalt components to the corresponding metalsand to insure a uniform and finely divided dispersion of these metalliccomponents throughout the carrier material, while maintaining the tincomponent in a positive oxidation state. Preferably substantially pureand dry hydrogen (i.e., less than 20 vol. ppm. H₂ O) is used as thereducing agent in this step. The reducing agent is contacted with theoxidized catalyst at conditions including a temperature of about 425° Cto about 650° C and a period of time of about 0.5 to 2 hours to reducesubstantially all of the platinum or palladium and cobalt components totheir elemental metallic state while maintaining the tin component in anoxidation state above that of the elemental metal. This reductiontreatment may be performed in situ as part of a start-up sequence ifprecautions are taken to predry the plant to a substantially water-freestate and if substantially water-free and hydrocarbon-free hydrogen isused.

As used herein, the expression cobalt component is intended to mean theportion of the cobalt component that is available for use inaccelerating the particular hydrocarbon conversion reaction of interest.For certain types of carrier materials which can be used in thepreparation of the instant catalytic composite, it has been observedthat a portion of the cobalt incorporated therein is essentiallybound-up in the crystal structure thereof in a manner which essentiallymakes it more a part of the refractory carrier material than acatalytically active component. Specific examples of this effect areobserved when the carrier material can form a spinel or spinel-likestructure with a portion of the cobalt component. When this effectoccurs, it is only with great difficulty that the portion of the cobaltbound-up with the support can be reduced to a catalytically active stateand the conditions required to do this are beyond the severity levelsnormally associated with hydrocarbon conversion conditions and are infact likely to seriously damage the necessary porous characteristics ofthe support. In the cases where cobalt can interact with the crystalstructure of the support to render a portion thereof catalyticallyunavailable, the concept of the present invention merely requires thatthe amount of cobalt added to the subject catalyst be adjusted tosatisfy the requirements of the support as well as the catalyticallyavailable cobalt requirements of the present invention. Against thisbackground then, the hereinbefore stated specifications for oxidationstate and dispersion of the cobalt component are to be interpreted asdirected to a description of the catalytically availble cobalt. On theother hand, the specifications for the amount of cobalt used are to beinterpreted to include all of the cobalt contained in the catalyst inany form.

The resulting reduced catalytic composite is preferably maintained in asulfur-free state during its preparation and use. The beneficialinteraction of the catalytically available cobalt component with theother ingredients of the catalyst is contingent upon the maintenance ofthe cobalt in a highly dispersed, readily reducible state in the carriermaterial. Surfur in the form of sulfide adversely interfers with boththe dispersion and reducibility of the cobalt, so presulfiding should beavoided. Once the catalyst has been exposed to hydrocarbon for asufficient period of time to lay down a protective layer of carbon orcoke on the catalyst, the sulfur sensitivity of the catalyst changesrather markedly and the presence of small amounts of sulfur can betolerated. Thus, contact of freshly reduced catalyst with sulfur canseriously damage the cobalt component and jeopardize the superiorperformance characteristics of the catalyst. However, once a protectivelayer of carbon is established on the catalyst, the sulfur deactivationeffect is less permanent and the sulfur can be purged from the catalystby exposure to a sulfur free hydrogen stream at 425° to 60° C.

According to the process of the present invention, an isomerizablehydrocarbon charge stock, preferably in admixture with hydrogen, iscontacted with a catalyst of the type hereinbefore described in ahydrocarbon isomerization zone. Contacting may be effected using thecatalyst in a fixed bed system, a moving bed system, a fluidized bedsystem, or in a batch type operation. In view of the danger of attritionloss of the valuable catalyst and of operational advantages it ispreferred to use a fixed bed system. In this system, a hydrogen-rich gasand the charge stock are preheated by suitable heating means to thedesired reaction temperature and then passed into an isomerization zonecontaining a fixed bed of the catalyst type previously characterized.The conversion zone may be one or more separate reactors with suitablemeans therebetween to insure that the desired isomerization temperatureis maintained at the entrance to each zone. It is to be noted that thereactants may be contacted with the catalyst bed in either upward,downward, or radial flow fashion, and that the reactants may be in theliquid phase, a mixed liquid-vapor phase, or a vapor phase whencontacted with the catalyst, with best results obtained in a vaporphase.

The process of this invention, utilizing the catalyst described abovefor isomerizing isomerizable olefinic or saturated hydrocarbons, ispreferably effected in a continuous down-flow fixed bed system. Onepreferred method is to pass the hydrocarbons continuously, preferablycommingled with about 0.1 to about 10 moles or more of hydrogen per moleof hydrocarbon, to an isomerization reaction zone containing thecatalyst, and to maintain the zone at proper isomerization conditionssuch as a temperature in the range of about 0° to about 425° C or moreand a pressure of about atmospheric to about 100 atmospheres or more.The hydrocarbon is passed over the catalyst at a liquid hourly spacevelocity (defined as volume of liquid hydrocarbon passed per hour pervolume of catalyst) of from about 0.1 to about 10 hr.⁻¹ or more. Inaddition, diluents such as argon, nitrogen, etc., may be present. Theisomerized product is continuously withdrawn, separated from the reactoreffluent, and recovered by conventional means such as fractionaldistillation, while the unreacted starting material may be recycled toform a portion of the feed stock.

The process of this invention for isomerizing an isomerizablealkylaromatic hydrocarbon is preferably effected by contacting thealkylaromatic, in a reaction zone containing the hereinbefore describedcatalyst, with a fixed catalyst bed by passing the hydrocarbon in adown-flow fashion through the bed, while maintaining the zone at properalkylaromatic isomerization conditions such a a temperature in the rangefrom about 0° C. to about 600° C. or more, and a pressure of atmosphericto about 100 atmospheres or more. The hydrocarbon is passed, preferably,in admixture with hydrogen at a hydrogen to hydrocarbon mole ratio ofabout 0.5:1 to about 20:1 or more, and at a liquid hourly hydrocarbonspace velocity of about 0.1 to about 20 hr.⁻¹ or more. Other inertdiluents such as nitrogen, argon, etc, may be present. The isomerizedproduct is continuously withdrawn, separated from the reactor effluentby conventional means including fractional distillation orcrystallization, and recovered.

The following illustrative embodiments are given to illustrate furtherthe preparation of the trimetallic catalytic composite utilized in theprocess of the present invention and the employment of the catalyst inisomerization of hydrocarbons. It is to be understood that the examplesare illustrative rather than restrictive.

ILLUSTRATIVE EMBODIMENT I

This example demonstrates a particularly good method of preparing thepreferred catalytic composite utilized in the process of the presentinvention.

A tin-containing alumina carrier material comprising 1.6 mm spheres isprepared by: forming an aluminum hydroxyl chloride sol by dissolvingsubstantially pure aluminum pellets in a hydrochloric acid solution,adding stannic chloride to the resulting sol in an amount selected toresult in a finished catalyst containing 0.2 weight percent tin, addinghexamethylenetetramine to the resulting tin-containing alumina sol,gelling the resulting solution by dropping it into a hot oil bath toform spherical particles of an aluminum hydrogel containing tin in aparticle size which is less than 100 Angstroms maximum chord length,aging and washing the resulting particles and finally drying andcalcining the aged and washed particles to form spherical particles ofgamma-alumina containing about 0.3 weight percent combined chloride anda uniform dispersion of about 0.2 weight percent tin in the form of tinoxide. Additional details as to this method of preparing the preferredcarrier material are given in the teachings of U.S. Pat. No. 2,620,314.

An aqueous impregnation solution containing chloroplatinic acid,cobaltous chloride and hydrogen chloride is then prepared. This solutionis then intimately admixed with the tin-containing gamma-aluminaparticles in amounts, respectively, calculated to result in a finalcomposite containing, on an elemental base, 0.3 weight percent platinum,1.0 weight percent cobalt and 0.2 weight percent tin. In order to insureuniform distribution of the metallic components throughout the carriermaterial, the amount of hydrogen chloride corresponds to about 3 weightpercent of the alumina particles. This impregnation step is performed byadding the carrier material particles to the impregnation mixture withconstant agitation. In addition, the volume of the solution isapproximately the same as the void volume of the carrier materialparticles. The impregnation mixture is maintained in contact with thecarrier material particles for a period of about one-half hour at atemperature of about 20° C. Thereafter, the temperature of theimpregnation mixture is raised to about 106° C and the excess solutionis evaporated in a period of about 1 hour. The resulting dried particlesare then subjected to a calcination treatment in an air atmosphere at atemperature of about 495° C for about 1 hour. The calcined spheres arethen contacted with an air stream containing H₂ O and HCl in a moleratio of about 30.1 for about 2 hours at 525° C in order to adjust thehalogen content of the catalyst particles to a value of about 1.09weight percent.

The resulting catalyst particles are analyzed and found to contain, onan elemental basis, about 0.3 weight percent platinum, about 1.0 weightpercent cobalt, about 0.2 weight percent tin and about 1.09 weightpercent chloride. For this catalyst, the atomic ratio of tin to platinumis 1.1:1 and the atomic ratio of cobalt to platinum is 11:1.

Thereafter, the catalyst particles are subjected to a dry prereductiontreatment designed to reduce the platinum and cobalt components to theelemental state while maintaining the tin component in a positiveoxidation state by contacting them for one hour with a substantiallypure hydrogen stream containing less than 5 vol. ppm. H₂ O at atemperature of about 565° C, a pressure slightly above atmospheric and aflow rate of the hydrogen stream through the catalyst particlescorresponding to a gas hourly space velocity of about 720 hr⁻¹.

ILLUSTRATIVE EMBODIMENT II

A portion of the spherical trimetallic catalyst particles producted bythe method described in Illustrative Embodiment I is loaded into acontinuous, fixed bed isomerization plant of conventional design. Thecharge stock, containing on a weight percent basis, 20.0% ethylbenzene,10.0% para-xylene, 50.0% meta-xylene, and 20.0% ortho-xylene iscommingled with about 8 moles of hydrogen per mole of hydrocarbon,heated to 400° C, and continuously charged at 4.0 hr⁻¹ liquid hourlyspace velocity (LHSV) to the reactor which is maintained at a pressureof 30 atm absolute. The resulting product evidences essentiallyequilibrium conversion to para-xylene with only insignificant amounts ofcracked products thus indicating an efficient alkylaromaticisomerization catalyst.

ILLUSTRATIVE EMBODIMENT III

A portion of the catalyst produced by the method of IllustrativeEmbodiment I is placed in a continuous flow, fixed bed isomerizationplant of conventional design as utilized in Illustrative Embodiment II.Substantially pure meta-xylene is used as a charge stock. The chargestock is commingled with about 8 moles of hydrogen per mole ofhydrocarbon, heated to about 390° C, and continuously charged to thereactor which is maintained at a pressure of about 21 atm. Substantialconversion of meta-xylene to para-xylene is obtained.

ILLUSTRATIVE EMBODIMENT IV

A catalyst identical to that produced in Illustrative Embodiment I butcontaining only 0.40 weight percent combined chloride is used toisomerize 1-butene in an appropriate isomerization reactor, at a reactorpressure of about 35 atm and a reactor temperature of about 140° C.Substantial conversion to 2-butene is observed.

ILLUSTRATIVE EMBODIMENT V

The same catalyst as utilized in Illustrative Embodiment IV is chargedto an appropriate, continuous isomerization reaction of conventionaldesign maintained at a reactor pressure of about 70 atm and a reactortemperature of about 180° C 3-methyl-1-butene is continuously passed tothis reactor with substantial conversion to 2-methyl-2-butene beingobserved.

ILLUSTRATIVE EMBODIMENT VI

A catalyst, identical to that catalyst produced in IllustrativeEmbodiment I except that the gamma-alumina particles are contacted withhydrogen fluoride to provide a 2.9 weight percent combined fluoridecontent in the catalyst, is placed in an appropriate continuousisomerization reactor of conventional design maintained at a reactorpressure of about 21 atm psig, and a reactor temperature of about 200°C. Normal hexane is continuously charged to the reactor and substantialconversion to 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylpentane,and 3-methylpentane is observed.

ILLUSTRATIVE EMBODIMENT VII

A portion of the catalyst prepared in Illustrative Embodiment I isplaced in an appropriate continuous isomerization apparatus and used toisomerize normal butane at a reactor pressure of 21 psig, a 0.5 hydrogento hydrocarbon mole ratio, a 1.0 liquid hourly space velocity, and areactor temperature of 230° C. Substantial conversion of normal butaneto isobutane is observed.

ILLUSTRATIVE EMBODIMENT VIII

A portion of the catalyst prepared in Illustrative Embodiment I isplaced in an appropriate continuous isomerization reactor maintained ata reactor temperature of about 210° C and a reactor pressure of about 18atm. Methylcyclopentane is continuously passed to this reactor with asubstantial conversion to cyclohexane being observed.

ILLUSTRATIVE EMBODIMENT IX

A sample of catalyst is prepared in a manner identical to that employedin Illustrative Embodiment I up to and including the calcination step.The calcined particles are then placed in a glass lined, rotatingautoclave with anhydrous aluminum chloride. Three weights of AlCl₃ areadded for each four weights of calcined particles. The autoclave issealed, evacuated, then pressured with H₂ to 3 atm, absolute. Theautoclave is heated to 300° C for 2 hours, with rotation. The calcinedcomposite experienced a weight gain of 15 weight percent. Theseparticles were then reduced in the manner disclosed in IllustrativeEmbodiment I.

ILLUSTRATIVE EMBODIMENT X

Catalyst prepared in Illustrative Embodiment IX is tested forisomerization of normal butane at a 0.5 H₂ to hydrocarbon ratio, 1.0LHSV, and reactor temperature of 150° C. Substantial conversion ofnormal butane to isobutane is observed.

ILLUSTRATIVE EMBODIMENT XI

Catalyst is prepared as in Illustrative Embodiment I up to and includingthe calcination step. About 100 g of calcined particles are then placedin a vertical Pyrex tube with a bed of 30 g of AlCl₃ on top. H₂ at 250°C and gas hourly space velocity of 250 is passed over the bed untilcomplete sublimation of AlCl₃ is observed. The temperature is thenincreased to 300° C for 30 minutes. The particles are then cooled underN₂ gas flow and reduced as described in Illustrative Embodiment I.

ILLUSTRATIVE EMBODIMENT XII

Catalyst prepared in Illustrative Embodiment XI is tested as disclosedin Illustrative Embodiment X. Substantial conversion of normal butane toisobutane is observed.

We claim as our invention:
 1. A process for isomerizing an isomerizablenaphthalene hydrocarbon selected from the group consisting of C₅ to C₉naphthenes which comprises contacting said hydrocarbon at isomerizationconditions with a catalyst comprising a porous carrier materialcontaining, on an elemental basis, 0.01 to 2 wt. % platinum group metal,0.1 to 5 wt. % cobalt, 0.01 to 5 wt. % tin and 0.1 to 10 wt. % halogen,wherein substantially all of the platinum group metal, cobalt and tinare uniformly dispersed throughout the porous carrier material, whereinsubstantially all of the platinum group metal and cobalt are present inthe elemental metallic state and wherein substantially all of the tin ispresent in an oxidation state above that of the elemental metal. 2.Process of claim 1 wherein the tin has a particle size with a maximumchord length less than 100 Angstroms.
 3. Process of claim 1 wherein theplatinum group metal is selected from the group of platinum andpalladium.
 4. Process of claim 1 wherein the porous carrier material isa refractory inorganic oxide.
 5. Process of claim 1 wherein therefractory inorganic oxide is alumina.
 6. Process of claim 1 wherein thehalogen is combined chloride.
 7. Process of claim 1 wherein the atomicratio of tin to platinum group metal is 0.1:1 to 13:1.
 8. Process ofclaim 1 wherein the atomic ratio of cobalt to platinum group metal is0.8:1 to 66:1.
 9. Process of claim 1 wherein substantially all of thetin is present as tin oxide.
 10. Process of claim 1 containing 0.05 to 1wt. % platinum, 0.5 to 2 wt. % cobalt, 0.05 to 1 wt. % tin, 0.5 to 1.5wt. % halogen.
 11. Process of claim 1 wherein the catalyst contains, onan elemental metal basis, a total metals content of 0.15 to 5 wt. %. 12.Process of claim 1 wherein the catalytic composite additionally contains1 to 100 wt. % of a Friedel-Crafts metal halide based on aFriedel-Crafts metal halide-free composite.
 13. Process of claim 1wherein the Friedel-Crafts metal halide is aluminum chloride. 14.Process of claim 1 wherein the isomerization conditions include atemperature of 0° to 425° C., a pressure of atmospheric to 100atmospheres, and a liquid hourly space velocity of 0.1 to
 10. 15.Process of claim 1 wherein the naphthene hydrocarbon is commingled with0.1 to 10 moles of hydrogen per mole of hydrocarbon.